222 PROCEEDINGS OF THE ACADEMY OF [DeC, 



of the shell is well rounded, while in floridana it is indistinctly trun- 

 cate. The interior has numerous small solid lumps. The beaks are 

 smooth. 



Length 8.7, alt. 8.3, diam. 5.2 mm. 



Livingston, Guatemala, A. A. Hinkley, 1913. Type, No. 107,532, 

 A. N. S. P. 



Eupera yucatanenenis minima n. subsp. 



The shell resembles E. yucatanensis in contour, having a very 

 narrow anterior and broad posterior end; of a uniform buff-corneous 

 tint, sometimes (seven out of thirty -one specimens examined) macu- 

 late with dark gray. It differs from E. singleyi by the narrower 

 anterior end and the more projecting beaks. 



Length 5, alt. 3.3, diam. 2.5 mm. 



Valles river, Valles, State of San Luis Potosi, Mexico, on the 

 under side of rocks in shallow water, where there is a strong current 

 in mid-stream (A. A. Hinkley). 



Probably a distinct species. E. yucatanensis measures : length 1 0, 

 alt. 7, diam. 5 mm. 

 Donax mediamericana n. sp. PI. XI, flg. lo. 



A species related to D. striata L., from which it differs by being 

 smaller, comparatively longer, the alt. being three-fifths of the 

 length; the angle between the anterior dorsal border and the pos- 

 terior keel is decidedly and constantly larger; the anterior end is 

 longer and tapers rapidly. The beaks are at the posterior four- 

 tenths of the length. The keel is not so strongly expressed as in 

 D. striata, and the posterior area is much more convex. The sur- 

 face is shining, sculptured about as in D. striata. There are many 

 radial riblets on the posterior end and extending on the valve about 

 to the middle, whence they diminish gradually to the anterior end. 

 The anterior-dorsal slope is almost smooth. The riblets crenulate 

 the basal edge near the posterior angle, but less strongly than in 

 D. striata. The teeth resemble those of D. striata except that the 

 laterals are lower and much less robust. 



The color is variable: white throughout; pink with concentric 

 zones of a deeper shade, the interior pink, often violet at the ends; 

 yellow, the interior white or pink and white, with violet ends; or 

 yellow with dull bluish zones and beaks, the interior deep violet. 



Length 22. alt. 12.5, diam. 7.9 mm. cotype. 

 " 21.5, " 13. " 7.9 " 

 " 24.9, " 15. '' 8.3 " 

 " 25. " 14.9, '' 9 



